# Dual Malignancies Discovered: A Rare Case of Malignant Peritoneal Epithelioid Mesothelioma and Lung Adenocarcinoma

## TL;DR

A rare case of two cancers, peritoneal mesothelioma and lung adenocarcinoma, was diagnosed in a 73-year-old woman with no risk factors.

## Contribution

Highlights a rare dual malignancy case with no asbestos exposure or smoking history.

## Key findings

- Patient had malignant peritoneal epithelioid mesothelioma and lung adenocarcinoma simultaneously.
- Diagnosis was confirmed using histology and immunocytochemistry.
- Case emphasizes the importance of thorough pathology review for rare dual cancers.

## Abstract

Clinicians diagnosing malignant peritoneal epithelioid mesothelioma (MPM or MPeM) have historically had challenges due to the low incidence of the disease, as well as the often vague symptomatology that patients present with. Newer advances in technology, specifically in immunocytochemistry, have provided a clearer path to diagnosis. Additionally, malignant mesotheliomas must be differentiated from carcinomas. This is done via histology, immunocytochemistry, as well as a careful incorporation of the patient’s clinical history. In this case, we present an asymptomatic 73-year-old non-smoker female with no past medical history of asbestos exposure. She was diagnosed with MPM following a routine abdominal hernia repair. Subsequent workup revealed a lung infiltrate that was successfully biopsied and resected, evidently found to be adenocarcinoma. A careful review of the resulting pathology, as well as the interpretation of immunocytochemistry, supported the notion that the patient had two independent malignant processes occurring at once. This case underscores the rarity of two similar, yet distinct cancers, as well as epidemiology, symptomatology, histology, immunocytochemistry, and prognosis.